Battery management system

ABSTRACT

The disclosed battery management system generally includes at least one bi-directional balancing circuit and a power supply including a first battery module and a second battery module, each having at least one battery cell. The balancing circuit may be configured to transfer excess charge from one or more battery cells of the first battery module to one or more battery cells of the second battery module. By redistributing the level of charge within one or more battery cells, the balancing circuit can cause the overall charge of a power supply to last longer by taking advantage of excess charge found within one or more battery cells. Additionally, the balancing circuit may be connected to a bus bar that may be utilized to power additional accessories within a vehicle.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 U.S.C. 119(e) toapplication Ser. No. 62/398,857 titled “Battery Management System” andfiled on Sep. 23, 2016, as well as application Ser. No. 62/512,553titled “Battery Management System” and filed on May 30, 2017, theentirety of both applications incorporated herein by reference.

This application is related to co-pending U.S. patent application Ser.No. ______ (Attorney Docket Number 123-1049), filed on Sep. 21, 2017,and U.S. patent application Ser. No. ______ (Attorney Docket Number123-1051), filed on Sep. 21, 2017, which are both hereby incorporated intheir entirety.

BACKGROUND OF THE INVENTION

The present invention relates generally a battery management system.Specifically, the present disclosure relates to a battery managementsystem used in heavy duty electric vehicles used in mining operations.

Large, high voltage batteries are used in heavy duty applications, suchas in electric and hybrid vehicles used in underground mining. Thesebatteries often include multiple battery modules each containing a setof individual battery cells.

Because of the inconsistent temperatures and rough conditions in whichthese batteries are used, these battery cells often begin to weaken atdifferent rates. The weaker battery cells within a battery module tendto leak charge quicker than other batteries in the same battery module.This leaking causes the individual battery cells within a battery moduleto have varying charges. The type of batteries used in heavy dutyapplications are prone to inefficiency, overheating, and/or other issueswhen the individual battery cells within a battery module have differentcharges. Battery balancing systems are employed to help make batteriesrun more efficiently for a longer period of time.

There is a need in the art for a system and method that addresses theshortcomings of the prior art discussed above.

SUMMARY

The disclosed battery management system generally includes at least onebi-directional balancing circuit and a power supply including a firstbattery module and a second battery module, each having at least onebattery cell. Because battery cells sometimes tend to lose charge atdifferent rates, the battery cell(s) within the first battery module mayhave a different level of charge than the battery cell(s) within thesecond battery module. If the first and second battery modules were usedwithout balancing the charges of the individual cells of each batterymodule, the amount of electrical energy provided by the power supplywould be limited by the individual battery cell having the lowestcharge. The balancing circuit can increase the amount of electricalcharge provided by the power supply to be higher than the level ofcharge of the battery cell having the lowest charge. The balancingcircuit may be configured to transfer excess charge from one or morebattery cells of a first battery module to one or more battery cells ofthe second battery module. By redistributing the level of charge withinone or more battery cells, the balancing circuit can cause the overallcharge of a power supply to last longer by taking advantage of excesscharge found within one or more battery cells.

In one aspect, the disclosure provides a battery management system,comprising a first battery module, a second battery module, and abi-directional balancing circuit. The first battery module has a firstplurality of battery cells, including a first battery cell and a secondbattery cell. The second battery module has a second plurality ofbattery cells, including a third battery cell and a fourth battery cell.The bi-directional balancing circuit is electrically connected to boththe first battery cell and the third battery cell. The bi-directionalbalancing circuit is an integrated circuit configured to transfer chargebetween at least the first battery cell and the third battery cell.

In another aspect, the disclosure provides a battery management system,comprising a first battery module, a second battery module, and abi-directional balancing circuit. The bi-directional balancing circuitis electrically connected to at least one battery cell of the firstplurality of battery cells and at least one battery cell of the secondplurality of battery cells. The bi-directional balancing circuit is anintegrated circuit configured to transfer charge between the at leastone battery cell of the first plurality of battery cells and the atleast one battery cell of the second plurality of battery cells.

In another aspect, the disclosure provides a battery management system,comprising a first battery module, a second battery module, and abi-directional balancing circuit. The bi-directional balancing circuitis electrically connected to at least one battery cell of the firstplurality of battery cells and at least one battery cell of the secondplurality of battery cells. The bi-directional balancing circuit is anintegrated circuit configured to balance the level of charge amongstboth the first plurality of battery cells and the second plurality ofbattery cells.

Other systems, methods, features and advantages of the embodiments willbe, or will become, apparent to one of ordinary skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description and this summary, bewithin the scope of the embodiments, and be protected by the followingclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the embodiments. Moreover, in the figures, likereference numerals designate corresponding parts throughout thedifferent views.

FIG. 1 shows a mining vehicle employing a battery management system,including a first battery module and a second battery module;

FIG. 2 shows an isometric view of the first battery module and thesecond battery module separate from the vehicle;

FIG. 3 shows a representation of the charge carried by the individualbattery cells within the first battery module and the second batterymodule before the individual battery cells of both modules are balanced;

FIG. 4 shows a representation of the charge carried by the individualbattery cells within the first battery module and the second batterymodule after the individual battery cells of both modules are balanced;

FIG. 5 shows a block diagram of an embodiment of the battery managementsystem;

FIG. 6 shows of a representation of the charge carried by individualbattery cells and a bus bar before the cells are balanced;

FIG. 7 shows of a representation of the charge carried by individualbattery cells and a bus bar after the cells are balanced; and

FIG. 8 shows an embodiment of a schematic representation of a batterymanagement system.

DETAILED DESCRIPTION

FIG. 1 shows a mining vehicle 106 employing a battery management system.The battery management system includes a bi-directional balancingcircuit and a power supply including a plurality of battery modules, orbattery stacks. FIG. 5, which is discussed in more detail below, shows ablock diagram of an embodiment of the battery management system. Theplurality of battery modules shown in FIGS. 1-5 are a first batterymodule 100 and a second battery module 200. FIG. 1 shows first batterymodule 100 and a second battery module 200 disposed within miningvehicle 106. As shown in FIG. 2, first battery module 100 and secondbattery module 200 each have at least one battery cell, and areelectrically connected to an engine 104 of vehicle 106. First batterymodule 100 and second battery module 200 supply electrical power toengine 104. The battery management system balances the battery cellswithin first battery module 100 and second battery module 200 when thebattery cells have differing levels of charge. For example, the batterymanagement system balances the battery cells when a damaged batterymodule in a vehicle, such as mining vehicle 106, is replaced withanother battery module, such as first battery module 100. FIGS. 3 and 4,also discussed below, demonstrate how the battery management systembalances the battery cells.

FIG. 2 shows an isometric view of first battery module 100 and secondbattery module 200 separate from vehicle 106. As shown in FIG. 2, firstbattery module 100 includes a first plurality of battery cells. Thefirst plurality of battery cells in this example includes 24 batterycells, which include the following: cell 1, cell 2, cell 3, cell 4, cell5, cell 6, cell 7, cell 8, cell 9, cell 10, cell 11, cell 12, cell 13,cell 14, cell 15, cell 16, cell 17, cell 18, cell 19, cell 20, cell 21,cell 22, cell 23, and cell 24.

Second battery module 200 includes a second plurality of battery cells.The second plurality of battery cells in this example includes 24battery cells, which include the following: cell 25, cell 26, cell 27,cell 28, cell 29, cell 30, cell 31, cell 32, cell 33, cell 34, cell 35,cell 36, cell 37, cell 38, cell 39, cell 40, cell 41, cell 42, cell 43,cell 44, cell 45, cell 46, cell 47, and cell 48. The second plurality ofbattery cells are shown as being disposed within a container 202. Asshown in FIG. 5, the battery cells of the first plurality of batterycells are connected to one another in series. First battery module 100and second battery module 200 are electrically connected together inseries, as shown in FIG. 5 and described in more detail below.

The first plurality of battery cells are shown as being disposed withina container 102 of first battery module 100. The second plurality ofbattery cells are shown as being disposed within a container 202 ofsecond battery module 200. The containers of the battery modules mayinclude openings for wires to extend through and reach other components,such as a balancing circuit of another battery module. FIG. 2 shows anopening 204.

FIGS. 3 and 4 show an example of how the individual battery cells of twoor more battery modules are actively balanced. In this example, firstbattery module 100 and second battery module 200 are being used to powervehicle 106. To demonstrate how the charges of the individual batterycells are balanced, FIGS. 3 and 4 show a representation of the batterycharges of the individual battery cells of first and second batterymodules before and after balancing. It is understood that the batterycells shown in FIGS. 3 and 4 are the same battery cells shown in FIG. 2.The charge of the battery cells shown in FIGS. 3 and 4 are given inpercentages. The percentage is based on the charging capacity of thebatteries. Over time, the charging capacity of battery cells change. Thepercentage of the battery cells shown in the example of FIGS. 3 and 4are based on the present charging capacity of the battery cells, ratherthan the percentage of the battery cells' original charging capacity.

FIG. 3 shows a representation of the charge carried by the individualbattery cells within first battery module 100 and second battery module200 before the battery cells are balanced. FIG. 4 shows a representationof the charge carried by the individual battery cells within firstbattery module 100 and second battery module 200 after the battery cellsare balanced. In the example of FIGS. 3 and 4, first battery module 100is replacing another battery module (not shown) that has been taken outof a vehicle. Such a replacement is often made due to the strenuousconditions of heavy duty applications, such as underground mining,wearing out batteries. In the example shown in FIGS. 3 and 4, firstbattery module 100 was charged more recently than second battery module200, which was being used to power the vehicle before first batterymodule 100 was added to the bank of battery modules. As a result, secondbattery module 200 has less overall charge than first battery module100.

The individual battery cells within first battery module 100 havedifferent charges from one another. As explained before, subjecting thebattery cells to high temperatures causes the battery cells to weaken.As a result, the weakened battery cells leak charge. In certainapplications, individual battery cells are subject to varyingtemperatures. Accordingly, the battery cells of the battery module thatare subject to high temperatures may weaken before other battery cellsof the same battery module that are not subject to the same hightemperatures. For example, in the embodiment of FIG. 3, first batterymodule 100 was charged to 90% before being installed in vehicle 106.However, due to the weakness of some of the battery cells in comparisonto other battery cells, the individual battery cells of first batterymodule 100 have different levels of charge. In the example of FIG. 3,cell 9, cell 10, cell 11, cell 12, cell 21, cell 22, cell 23, and cell24 are 80% charged. Cell 1, cell 2, cell 3, cell 4, cell 5, cell 6, cell7, cell 8, cell 13, cell 14, cell 15, cell 16, cell 17, cell 18, cell19, and cell 20 are each charged 90%. Before first battery module 100and second battery module 200 are balanced, first battery module 100 has16 battery cells with 90% charge and 8 battery cells with 80% charge. Inthis example, the 8 battery cells having 80% charge are the weakestbatteries in first battery module 100.

Similar to first battery module 100, the individual battery cells withinsecond battery module 200 have different charges from one another.Because second battery module 200 was being used to power vehicle 106before first battery module 100 was added to the bank of batterymodules, FIG. 3 shows the second plurality of battery cells as havingless charge than the first plurality of battery cells. FIG. 3 shows cell25, cell 26, cell 37, and cell 38 as each being 50% charged. FIG. 3shows cell 27, cell 28, cell 29, cell 30, cell 31, cell 32, cell 33,cell 34, cell 35, cell 36, cell 39, cell 40, cell 41, cell 42, cell 43,cell 44, cell 45, cell 46, cell 47, and cell 48 as each being 60%charged. Before first battery module 100 and second battery module 200are balanced, second battery module 200 has 20 battery cells with 60%charge and 4 battery cells with 50% charge. In this example, the 4battery cells having 50% charge are the weakest battery cells in secondbattery module 200 and are the weakest battery cells amongst the firstplurality of battery cells and the second plurality of battery cells.

If the first and second battery modules were used without balancing thecharges of the individual cells of each battery module, the batterypower supplied to the vehicle would be limited by the individual batterycell having the lowest charge. In this example, cell 25, cell 26, cell37, and cell 38 have the lowest charge (50%) of all of the individualbattery cells of both first battery module 100 and second battery module200. Accordingly, some of the charge in battery cells having highercharges than cell 25, cell 26, cell 37, and cell 38 goes unused. Forexample, cell 1 starts out 90% charged and ends with 40% charge. This40% of charge capacity goes unused. In other words, cell 1 is left withan excess charge of 40%. With the disclosed battery management system,rather than letting excess energy go unused, this excess charge of 40%is utilized by distributing this excess charge amongst battery cellshaving less charge than cell 1. In the same manner, the disclosedbattery management system distributes the excess charge of allindividual batteries between first battery module 100 and second batterymodule 200. This means that excess charge from a battery cell in firstbattery module 100 can be distributed to a battery cell in secondbattery module 200. Conversely, the excess charge from a battery cell insecond battery module 200 can be distributed to a battery cell in firstbattery module 100.

The excess charge for each battery cell within a bank of battery modulesis the amount of charge above the charge of the battery cell having thelowest charge. In the example of FIGS. 3 and 4, the excess charge foreach battery cell within first battery module 100 and second batterymodule 200 is the amount of charge that is above 50%. As stated before,the excess charge in cell 1 is 40%. Because cell 2, cell 3, cell 4, cell5, cell 6, cell 7, cell 8, cell 13, cell 14, cell 15, cell 16, cell 17,cell 18, cell 19, and cell 20 are also 90% charged, these same cellsalso have an excess charge of 40%. Similarly, because cell 9, cell 10,cell 11, cell 12, cell 21, cell 22, cell 23, and cell 24 are 80%charged, these same cells have an excess charge of 30%. And because cell27, cell 28, cell 29, cell 30, cell 31, cell 32, cell 33, cell 34, cell35, cell 36, cell 39, cell 40, cell 41, cell 42, cell 43, cell 44, cell45, cell 46, cell 47, and cell 48 are 60% charged, these same cells havean excess charge of 10%.

The disclosed battery management system distributes the excess chargefrom one or more individual battery cells to one or more battery cellshaving less charge. Taking energy from the battery cells having highercharges, and giving this energy to battery cells having lower chargesbrings the charge of all of the battery cells closer to being the same.In the example of FIGS. 3 and 4, the excess charge for individualbattery cells within first battery module 100 and second battery module200 is discharged from the batteries having excess charge and isdistributed among the individual battery cells having lower charges.More particularly, the excess charge is distributed amongst theindividual battery cells such that all of the individual battery cellsof both first battery module 100 and second battery module 200 areequally charged. FIG. 4 shows the individual battery cells of firstbattery module 100 and second battery module 200 being 72.5% charged.

Balancing the charge within each battery module by balancing the cells,and within each pack of modules by balancing the state of charge of themodules, increases power efficiency in the equipment, and extends thelife of each battery module. Being able to monitor the charge conditionand balance the cells or modules also extends the operating cycle of theequipment to minimize downtime necessary to replace a battery module.Each battery module may be provided with an identifier, and a monitoringsystem may be employed to track the modules through their lifecycles byrecording the states of charge, the rate of depletion, replacementcycles, etc. By tracking each battery module, it is possible to identifythose modules which are losing charge more rapidly or less efficient tohave those be serviced on a cell by cell basis or taken out of service.

The battery management system generally includes at least onebi-directional balancing circuit and a power supply including at leasttwo battery modules each having at least one battery cell. As previouslymentioned, FIG. 5 shows a block diagram of an embodiment of the batterymanagement system. In this exemplary embodiment, at least two batterycells are electrically connected to one another in series within asingle module. More specifically, FIG. 5 shows cell 1, cell 2, cell 3,cell 4, cell 5, cell 6, cell 7, cell 8, cell 9, cell 10, cell 11, cell12, cell 13, cell 14, cell 15, cell 16, cell 17, cell 18, cell 19, cell20, cell 21, cell 22, cell 23, and cell 24 all electrically connected toone another in series such that the individual battery cells cantogether supply electrical power to vehicle 106.

The battery management system shown in FIG. 5 includes a plurality ofintegrated balancing circuits, including first balancing circuit 500,second balancing circuit 502, third balancing circuit 504, fourthbalancing circuit 506, fifth balancing circuit 512, sixth balancingcircuit 514, seventh balancing circuit 516, and eighth balancing circuit518. The plurality of bi-directional balancing circuits each comprise anintegrated circuit configured to transfer charge between the at leastone battery cell of the first plurality of battery cells and the atleast one battery cell of the second plurality of battery cells. Theexemplary balancing circuits are configured to implement a balancingalgorithm to balance the charge amongst the individual battery cells ofthe first plurality of battery cells and the second plurality of batterycells.

In this exemplary embodiment, at least two battery cells of a singlemodule are electrically connected to a bi-directional balancing circuit.More specifically, FIG. 5 shows cell 1, cell 2, cell 3, cell 4, cell 5,and cell 6 all electrically connected to a first balancing circuit 500.FIG. 5 shows cell 7, cell 8, cell 9, cell 10, cell 11, and cell 12 allelectrically connected to a second balancing circuit 502. FIG. 5 showscell 13, cell 14, cell 15, cell 16, cell 17, and cell 18 allelectrically connected to a third balancing circuit 504. FIG. 5 showscell 19, cell 20, cell 21, cell 22, cell 23, and cell 24 allelectrically connected to a fourth balancing circuit 506.

In this exemplary embodiment, at least two battery cells of a singlemodule are electrically connected to a monitoring circuit. Morespecifically, FIG. 5 shows cell 1, cell 2, cell 3, cell 4, cell 5, cell6, cell 7, cell 8, cell 9, cell 10, cell 11, and cell 12 are allelectrically connected to a first monitoring circuit 508. Cell 13, cell14, cell 15, cell 16, cell 17, cell 18, cell 19, cell 20, cell 21, cell22, cell 23, and cell 24 are all electrically connected to a secondmonitoring circuit 510.

Regarding the battery cells of second battery module 200, FIG. 5 showscell 25, cell 26, cell 27, cell 28, cell 29, cell 30, cell 31, cell 32,cell 33, cell 34, cell 35, cell 36, cell 37, cell 38, cell 39, cell 40,cell 41, cell 42, cell 43, cell 44, cell 45, cell 46, cell 47, and cell48 are all electrically connected to one another in series. FIG. 5 showscell 25, cell 26, cell 27, cell 28, cell 29, and cell 30 allelectrically connected to a fifth balancing circuit 512. FIG. 5 showscell 31, cell 32, cell 33, cell 34, cell 35, and cell 36 allelectrically connected to a sixth balancing circuit 514. FIG. 5 showscell 37, cell 38, cell 39, cell 40, cell 41, and cell 42 allelectrically connected to a seventh balancing circuit 516. FIG. 5 showscell 43, cell 44, cell 45, cell 46, cell 47, and cell 48 allelectrically connected to a eighth balancing circuit 518.

FIG. 5 shows cell 25, cell 26, cell 27, cell 28, cell 29, cell 30, cell31, cell 32, cell 33, cell 34, cell 35, cell 36 are all electricallyconnected to a third monitoring circuit 520. Cell 37, cell 38, cell 39,cell 40, cell 41, cell 42, cell 43, cell 44, cell 45, cell 46, cell 47,and cell 48 are all electrically connected to a fourth monitoringcircuit 522.

In the exemplary embodiment shown in FIG. 5, at least one battery cellof first battery module 100 is electrically connected to a battery cellof second battery module 200 in series. More specifically, cell 1 iselectrically connected to cell 25 in series. As a result, the firstplurality of battery cells are electrically connected to the secondplurality of battery cells in series.

FIG. 5 shows the battery management system as including a microprocessor524. Microprocessor 524 is in serial communication with all of thebalancing circuits and monitoring circuits. Specifically, firstbalancing circuit 500, second balancing circuit 502, third balancingcircuit 504, and fourth balancing circuit 506 are in serialcommunication with microprocessor 524. Fifth balancing circuit 512,sixth balancing circuit 514, seventh balancing circuit 516, and eighthbalancing circuit 518 are in serial communication with microprocessor524. First monitoring circuit 508 and second monitoring circuit 510 arein serial communication with microprocessor 524. Third monitoringcircuit 520 and fourth monitoring circuit 522 are in serialcommunication with microprocessor 524.

FIG. 5 shows all of the monitoring circuits and balancing circuits asbeing in serial communication with one another. More specifically, firstmonitoring circuit 508 and second monitoring circuit 510 are in serialcommunication with one another. Third monitoring circuit 520 and fourthmonitoring circuit 522 are in serial communication with one another.First balancing circuit 500, second balancing circuit 502, thirdbalancing circuit 504, and fourth balancing circuit 506 are all inserial communication with one another. Fifth balancing circuit 512,sixth balancing circuit 514, seventh balancing circuit 516, and eighthbalancing circuit 518 are all in serial communication with one another.

First monitoring circuit 508 and second monitoring circuit 510 are inserial communication with third monitoring circuit 520 and fourthmonitoring circuit 522 via microprocessor 524. First balancing circuit500, second balancing circuit 502, third balancing circuit 504, andfourth balancing circuit 506 are in serial communication with fifthbalancing circuit 512, sixth balancing circuit 514, seventh balancingcircuit 516, and eighth balancing circuit 518 via microprocessor 524.First monitoring circuit 508, second monitoring circuit 510, thirdmonitoring circuit 520, and fourth monitoring circuit 522 are in serialcommunication with first balancing circuit 500, second balancing circuit502, third balancing circuit 504, fourth balancing circuit 506, fifthbalancing circuit 512, sixth balancing circuit 514, seventh balancingcircuit 516, and eighth balancing circuit 518 via microprocessor 524.

Specifically, first balancing circuit 500 is electrically connected tothird balancing circuit 504 in series. As a result, because the cells offirst battery module 100 are electrically connected to first balancingcircuit 500 in series, and because the cells of second battery module200 are electrically connected to third balancing circuit 504 in series,the battery cells of first battery module 100 are electrically connectedto the battery cells of second battery module 200 in series. Theseelectrical connections between the balancing circuits and the batterycells within first battery module 100 and second battery module 200allow energy to be transferred to and from the battery cells.Accordingly, the excess energy of cell 1, which is in first batterymodule 100, can be transferred to cell 13, which is in second batterymodule 200.

The bi-directional nature of the balancing circuit and the electricalconnection between the individual battery cells and the balancingcircuits allow the balancing circuits to discharge and charge theindividual battery cells, as well as transfer charge between theindividual battery cells, in the manner discussed above with respect toFIGS. 3 and 4. The serial communication between the individual batterycells and the monitoring circuits allows the monitoring circuits tomonitor the voltage and temperature of the individual battery cellswithin first battery module 100 and second battery module 200. Theserial communication between microprocessor controls the balancingcircuits and the monitoring circuits.

The balancing circuits shown in FIG. 5 of the present applicationinclude transformers and resistors. In other embodiments, the balancingcircuits may be configured as buck-boost converters and includeinductors, switches, diodes, capacitors or other components of abuck-boost converter.

The monitoring circuits shown in FIG. 5 comprise dedicated monitoringcircuits configured to monitor the temperature and voltage of each ofthe individual battery cells.

While the balancing circuits shown in FIG. 5 of the present applicationinclude transformers and resistors, it is understood that differentembodiments of the battery management system may include a balancingcircuit having different components. For example, the battery managementsystem may include a balancing circuit having one or more currentsensors. Additionally, other embodiments may include the same componentsof the exemplary embodiment rearranged in a different configuration.

The battery management system may include one or more balancing circuitsthat are configured to balance a plurality of battery cells according toan algorithm implemented by a microprocessor. In some embodiments, thebalancing circuit may handle all of the monitoring functions. In otherembodiments, as demonstrated by the exemplary example of FIGS. 1-5, thebattery management system may include dedicated monitoring circuit(s)that may provide more precise voltage monitoring.

While the exemplary embodiment shown in FIG. 5 shows 8 balancingcircuits, it is understood that other embodiments may include adifferent number of balancing circuits. For example, a batterymanagement system according to an embodiment of the present applicationmay include one balancing circuit that is in serial communication withall of the battery cells of a battery management system. In anotherexample, a battery management system according to an embodiment of thepresent application may include 2 balancing circuits that are each inserial communication with half of the battery cells of a batterymanagement system. One variation of this example may include a firstbalancing circuit that communicates with each of the battery cells of afirst battery module and a second balancing circuit that communicateswith each of the battery cells of a second battery module. In someembodiments, the battery management system may include as many balancingcircuits as there are battery modules. In some embodiments, the batterymanagement system may include as many balancing circuits as there arebattery cells. The number of balancing circuits may be selecteddepending on a variety of factors. For example, the number of balancingcircuits may be selected based on the number of battery cells that thebalancing circuits are each capable of balancing and the number ofbattery cells within the battery management system. The number ofbalancing circuits may range from one balancing circuit to 48 balancingcircuits.

While the exemplary embodiment shown in FIG. 5 shows 4 monitoringcircuits, it is understood that other embodiments may include adifferent number of monitoring circuits. For example, a batterymanagement system according to an embodiment of the present applicationmay include one monitoring circuit that is in serial communication withall of the battery cells of a battery management system. In anotherexample, a battery management system according to an embodiment of thepresent application may include 2 monitoring circuits that are each inserial communication with half of the battery cells of a batterymanagement system. One variation of this example may include a firstmonitoring circuit that communicates with the battery cells of a firstbattery module and a second monitoring circuit that communicates withthe battery cells of a second battery module. In some embodiments, thebattery management system may include as many monitoring circuits asthere are battery cells. The number of monitoring circuits may beselected depending on a variety of factors. For example, the number ofmonitoring circuits may be selected based on the number of battery cellsthat the monitoring circuits are each capable of monitoring and thenumber of battery cells within the battery management system. The numberof monitoring circuits may range from one monitoring circuit to 48monitoring circuits.

The connections between the features of the battery management systemmay be placed in communication with each other in a variety of differentways. For example, individual wires may be used to electricallyconnecting features. In another example, one or more communication busescould be used to provide communication between features of the circuits.

The shown embodiment demonstrates two battery modules powering anengine. It is understood that the disclosed battery management systemmay include more than two battery modules. For example, the batterymanagement system may include battery modules within a range of threeand 48 battery modules. The number of battery modules may be selectedbased on a variety of factors. For example, the number of batterymodules may be selected based on the physical size of the battery cells,the voltage of the battery cells, the number of battery cells, and theamount of energy required to power the engine or device being powered.

While the exemplary embodiment shown in FIG. 5 includes battery moduleshaving 24 battery cells each, it is understood that other embodimentsmay include a different number of battery cells within each module. Forexample, the battery management system may include 12 battery cells perbattery module. The number of battery cells per battery module may beselected depending on a variety of factors. For example, the number ofbattery cells per battery module may be selected based on the size ofthe container holding the battery modules and/or the amount of powerneeded in the application of the battery management system. The numberof battery cells per battery module may range from one battery cell to48 battery cells per battery module.

The battery modules of the battery management system may include acontainer or casing configured to receive and store a plurality ofbattery cells. For example, as shown in FIG. 2, first module 100 mayinclude first container 200, and second module 102 may include secondcontainer 202. The containers may have built-in components. For example,the containers may have electrical wiring and/or ports built intocontainers.

The battery cells may be stacked within the battery modules in variousconfigurations. For example, as shown in FIG. 2, the battery cells maybe stacked in two rows each containing 12 batteries. The configurationof the battery cells may be selected based on a variety of factors. Forexample, in some embodiments, the configuration of the battery cells maybe selected based on size and/or shape of the containers of the batterymodules.

It is understood that the battery management system may be configured aspart of an overall power management system in an underground mineenvironment. If used in conjunction with this type of power managementsystem, it is understood that any excess charge may be directed to aseparate power grid in the mine. Conversely, a power grid may beemployed as a source for the disclosed battery management system tofacilitate balancing the charge among battery cells or modules in apack.

While not shown in the exemplary embodiment, it is understood that thebattery management system may include a charger configured to charge theindividual battery cells of the system. The charger may be electricallyconnected to one or more of the battery cells of the first batterymodule and the second battery module to charge one or more of thebattery cells. The charger may be incorporated into a power managementsystem and operate from the separate power grid in a mine.

The upper and lower thresholds for charge may be programmed to desiredvalues. For example, in some embodiments, the upper threshold may be setto a value between 70% and 100%, such as 85%. In some embodiments, thelower threshold may be set to a value between 0% and 40%, such as 35%.It is noted that battery cells used in heavy industry, such as thebattery cells in the exemplary embodiment, are typically charged toabout 90% and are only allowed to discharge to about 30% to protect thecondition of the battery cell. In some embodiments, the batterymanagement system may include a microprocessor that implements the upperand lower thresholds for charge.

The type of batteries used in the battery module may include anysuitable type of battery, based on the application of the batterymanagement system. For example, in heavy duty industry applications,such as underground mining vehicles, Lithium-ion battery cells may beused. The voltage of the batteries used in the battery module mayinclude any suitable voltage. The voltage of the batteries may beselected based on a variety of factors. For example, the voltage of thebatteries may be selected based on the application of the batterymanagement system.

It is understood that the disclosed battery management system mayinclude battery modules that are used to power something other than anengine. For example, the battery modules may be used to poweraccessories in a vehicle, such as power steering or air conditioning.The excess charge in battery cells can be used to run an accessory. Insome embodiments, the excess charge in the battery cells may be used topower an accessory while simultaneously powering an engine or other maincomponent.

Referring now to FIG. 6, an isolated view of cell 1 and cell 25 isdepicted. Cell 1 and cell 25 are depicted in isolation for ease ofviewing and description. It should be recognized that cell 1 may belocated within first battery module 100 as depicted in FIG. 3, and cell25 may be located in second battery module 200 as depicted in FIG. 3. Inthis depiction, cell 1 and cell 25 have not been balance with eachother. Additionally, although depicted in isolation, it should berecognized that cell 1 and cell 25 may balance with respect to themodules and not necessarily with respect to each other. That is, thecharge of each cell when balanced may be about 72.5% as shown in FIG. 4.

In some embodiments, the balancing circuits may include buck-boostconverters, or buck converters or boost converters. For example, firstbalancing circuit 500 may include a buck-boost converter. Likewise,fifth balancing circuit 512 may include a buck-boost converter. In otherembodiments, separate buck-boost converters or other converters may beutilized. Buck-boost converters may be utilized to change an input oroutput voltage from a source. For example, cell 1 may have an outputvoltage of approximately 3 volts. The buck-boost converter may beutilized to increase or boost the output voltage to approximately 24volts. The buck-boost converters may be utilized to assist in balancingthe charges of the cells as previously discussed.

Cell 1 may send charge or energy through a buck-boost converter to a busbar. As shown in FIG. 6, cell 1 is connected to first converter 600 andcell 25 is connected to second converter 612. Although shown as separatecomponents, in some embodiments, first converter 600 may be incorporatedinto first balancing circuit 500 and second converter 612 may beincorporated into fifth balancing circuit 512. As shown, cell 1 sends a3 volt charge to first converter 600. First converter 600 converts the 3volt output from cell 1 to 24 volts. First converter 600 sends thisvoltage to bus bar 602. Therefore, bus bar 602 has a voltage of 24volts.

Although described as a 3 volt output from cell 1 with an output of 24volt output from first converter 600, it should be recognized thatvarious input and output voltages may be obtained. For example, in someembodiments the output voltage from cell 1 may be greater or less than 3volts. Additionally, the output voltage from first converter 600 may begreater or less than 24 volts. The buck-boost converters may be tuned orprogrammed to output a particular voltage depending on the particularneeds of an application or component.

Once at bus bar 602, the energy may now be used for various activitiesor applications. In some embodiments, the energy from bus bar 602 may besent to other cells within first battery module 100 or second batterymodule 200 to balance the cells with each other. In such embodiments,the voltage of bus bar 602 may be sent through a buck-boost converter toreduce the voltage to about 3 volts such that energy is transmitted tocells within second battery module 200. That is, in some embodiments,bus bar 602 may act as a pathway to other cells within first batterymodule 100 or second battery module 200 that have lower chargepercentages. As shown in FIG. 6, the voltage is sent through secondconverter 612 and converted to a 3 volt charge. This voltage from secondconverter 612 is sent to cell 25 to balance the charge of cell 25 withthat of the other cells within first battery module 100 and secondbattery module 200.

In other embodiments, the 24 volt energy from bus bar 602 may betransmitted to other components of mining vehicle 106 that utilize 24volt power supplies. For example, the 24 volt energy may be utilized topower accessories onboard mining vehicle 106. In some embodiments theaccessories may include, headlights, radio, hydraulics, control systems,power steering, air conditioning, or other components of mining vehicle106. By changing the voltage from 3 volts to 24 volts, various othercomponents within mining vehicle 106 may be powered using bus bar 602.

In some embodiments, the charge from cell 1 may be utilized to poweraccessories as well as balance the charge between cells of first batterymodule 100 and second battery module 200. That is, in some embodiments,a portion of the energy from cell 1 may be sent through first converter600 to bus bar 602 and to an accessory. Another portion of energy fromcell 1 may be sent through first converter 600, through bus bar 602,through second converter 612 and into cell 25 to charge cell 25.

Bus bar 602 may therefore act to as a pathway to reduce the charge ofgreater-charged cells of first battery module 100 while also poweringother components of mining vehicle 106. At the same time bus bar 602 maybe utilized to balance the charge amongst various cells within secondbattery module 200 and first battery module 100.

Referring now to FIG. 7, cell 1 and cell 25 are balanced withapproximately 70% charge. In this embodiment, the charge may be lowerthan the 72.5% charge shown in FIG. 4 because a portion of the chargefrom cell 1 was used by the accessories. Therefore, the balanced chargelevel between cell 1 and cell 25 may be lower than in the embodiment inwhich no accessories were powered.

The balanced charge level between cell 1 and cell 25 may be changeddepending on particular programming. For example, in some embodiments,the quantity of energy utilized by the accessories may be monitored andlimited. By limiting the quantity of energy utilized by the accessories,a given or known quantity of power or energy may be conserved withinfirst battery module 100 and second battery module 200. For example, insome embodiments, a lower level limit of charge may be set for the cellswithin first battery module 100 and second battery module 200. Once thecells within the battery modules reach the set charge limit energy mayno longer be sent to various accessories through bus bar 602.

In other embodiments, once balanced, cell 1 as well as cell 25 may bothsend energy to bus bar 602. That is, both cell 1 and cell 25 may sendcharge through the buck-boost converters to bus bar 602. Once energy orpower is sent to bus bar 602 the energy may be utilized by theaccessories. In this manner the accessories may be powered by bus bar602.

In some embodiments, utilizing accessories may decrease the timenecessary to balance various cells. By providing an additional load tothe cells, a greater quantity of charge may be removed from cell 1during balancing. By removing a greater quantity of charge from cell 1,cell 1 and cell 25 may become balance quicker than in other embodiments.

As discussed previously, in some embodiments the balancing circuits mayinclude buck-boost converters that may be utilized to increase anddecrease voltage. Buck-boost converters generally include inductors,capacitors, diodes and switches. Buck-boost converters may be used inplace of resistance-type voltage balancing. In resistance balancing aresistor may be used to lower the output voltage to charge a particularcell. The resistors intake voltage at a high level and output thevoltage at a lower level while also releasing heat. Because the cells ofa battery module do not function as well when hot, it is helpful toreduce the quantity of heat produced by a balancing system. Buck-boostconverters generate less heat than resistance-type balancing systems andtherefore allow a battery cell system incorporating a buck-boostconverter to perform more efficiently than embodiments that includeresistance-type balancing.

Additionally, the balancing circuits of the present embodiment may beable to accept greater amperage than an embodiment with resistance-typebalancing. In one embodiment, a resistor may be able to accept about 2amps of current whereas a similar balancing circuit may be able toaccept about 10 amps of current. By increasing the amperage into a cell,a cell may be able to be charged or balanced quicker than when chargedby lower amperage. Therefore, the time required to balance first batterymodule 100 with second battery module 200 utilizing balancing circuitsas described above may be less than a similar balancing system utilizingresistors.

Additionally, the time required to balance various cells utilizingbalancing circuits may be less than systems utilizing resistors becauseenergy is sent from a cell with a higher capacity to a cell with a lowercapacity. In resistance-type balancing, energy is sent to a resistor inorder to reduce the charge of a particular cell. The energy is consumedby the resistor and turned into heat. In the embodiment as describedpreviously, the energy is sent from cells of first battery module 100 tocells of second battery module 200. Because the cells within firstbattery module 100 are losing charge while the cells within secondbattery module 200 are gaining charge the time required to balance thecells may be reduced by at least half.

Referring now to FIGS. 6 and 7, the layout may be used to supplementexpensive DC to DC converters. Some embodiments may utilize a DC to DCconverter to power the various accessories of mining vehicle 106. Ratherthan using a DC to DC converter, cheaper buck-boosters and/or balancingcircuits as described above may be utilized to provide the neededvoltage to power the various accessories. For example, as shown in FIG.7, the balanced cells may each send energy or charge to bus bar 602 topower the accessories. In some embodiments, the quantity of charge orpower sent to bus bar 602 may be sufficient to power all of theaccessories such that a separate DC to DC converter is not necessary. Inother embodiments, the present layout of components may be utilized tosupplement a DC to DC converter. By utilizing the buck-boost system asdescribed above to supplement the needed voltage to various componentsthe size of the DC to DC converter may be able to be decreased. Asmaller DC to DC converter may reduce the overall cost of a machineincorporating the configuration of components as described above.

In some embodiments, the configuration as shown in FIGS. 6 and 7 may beutilized as a backup system in the event that a DC to DC converterfails. The backup power could be used to allow a user to move thevehicle or components to a separate location to be fixed. This backupsystem could decrease down time in a mining operation and increaseefficiency in fixing the problem by moving the mining vehicle to atechnician or work space. Further, because each cell of the modules mayinclude a buck-boost converter, additional redundancy is built into thesystem. For example, a buck-boost converter could fail on an individualcell without interfering with the ability of the cells to provide anadequate voltage to bus bar 602. Therefore, the accessories powered bybus bar 602 may continue to function even if individual failures occurwithin the cells of first battery module 100 or second battery module200.

In some embodiments, additional buck-boost converters may be utilized.In some embodiments, additional converters such as buck-boost, buck, orboost converters may be connected to bus bar 602. Additional convertersmay be able to increase the voltage to an even greater amount. Forexample, the 24 volts of bus bar 602 may be increased to 36 volts, 48volts, or even higher voltages. These greater voltages may be sent toother accessories or components that require greater than 24 volts. Insome embodiments, particular components may include separate convertersto increase or decrease the voltage from bus bar 602 to a particularspecialized amount. That is, rather than forming a new bus bar with aparticular voltage, the voltage may be directly pulled from bus bar 602and sent to an individual component requiring a certain voltage.

Referring now to FIG. 8 an embodiment of a battery management system isdepicted. As shown, a battery system may include multiple modules. Asdepicted, the battery system includes 16 modules. In other embodiments,a battery system may include greater or fewer than 16 modules. Thenumber of modules may be varied depending on the desired voltage oramperage output. Additionally, within each module are a number of cells.As shown, module 1 includes six cells. In other embodiments, 12 cells or24 cells may be utilized within each module. Additionally, in otherembodiments, the number of cells may be greater than 24 cells, less than6 cells, or between 6 cells and 24 cells.

Referring now to module 1, a possible layout of various cells isdepicted. Each of the cells may be connected to a chip such as LTC3300.This particular chip may be utilized to balance the voltage of each ofthe cells as described previously. Additionally, various other chipsbesides LTC3300 may be utilized to assist in balancing the charge orvoltages across the cells of a particular module. Further, as shown inFIG. 8, the bidirectional chips may be powered from the module. That is,module 1 may provide power to the bidirectional chips such that the chipmay then balance each of the cells within module 1.

In some embodiments, another portion of the battery management systemmay be powered by a source other than the module. For example, in someembodiments, a portion of the battery management system may be poweredby a 24 volt battery. This side of electronic circuitry may have a lowervoltage than the left side of the circuitry. As shown in FIG. 8, vehicle24V battery may be utilized to power various accessories and componentswithin mining vehicle 106. For example, in some embodiments the 24 voltbattery may be utilized to power headlights, communication components,and other components. The power produced by the modules however, may beutilized to provide power to an inverter and motor. The power producedby the modules may be used to rotate the tires of mining vehicle 106 aswell as operate any hydraulic components that may be located on miningvehicle 106.

In some embodiments, the voltage across various cells within each modulemay vary. In some embodiments, the cells within each module areconnected in series. Because voltage is additive in series thedifference of voltage from cell to cell may be greater than 700 volts.In other embodiments, the voltage different may be less than 700 volts.For example, in some embodiments, the cells within each module are inseries and the modules are in series with each other. The additivenature of voltage in series circuits may cause a large voltagedifferential between the first cell in the series and the last cell inthe series.

In some embodiments, the voltage of the various cells may be isolatedfrom other sources. As shown in FIG. 8, the voltage produce by module 1is isolated from the voltage produced by vehicle 24V battery.Transformer T1 may be utilized to isolate higher voltage electricityfrom lower voltage provided by a 24 volt battery. Isolating the voltagesupplies may allow for the energy produced by the modules to be used forpowering various components in addition to providing power to theinverter and motor. This may allow greater flexibility when designing asystem because the modules may now be able to produce lower voltage inaddition to higher voltage.

Further, in some embodiments, transformer T1 may be utilized to changethe voltage from the cells within module 1. As described previously, abuck, boost, or buck-boost converter may be utilized. The voltage maythen be transformed from a higher voltage to a 24 volt voltage to beused or stored within the 24 volt vehicle battery.

As described previously, excess charge or voltage may be sent through abuck-boost converter and to a bus bar. In this embodiment, the bus barmay include a 24 volt battery. Therefore, excess charge may be utilizedto charge or provide power to vehicle 24V battery. The 24 volt batterymay then be utilized to power various components and describedpreviously. Further, as described previously, during balancing of thecells rather than only directing energy to lower-charge cells, energymay also be sent to the 24 volt battery to supply energy to variousaccessories. This additional use of the excess charge from a particularcell may decrease the time necessary to balance the cells within eachmodule. That is because each cell may be able to output a greaterquantity of energy to various sources such as the 24 volt battery.Further, because there is another source for 24 volt supply to variouscomponents the size of the 24 volt battery to be reduced.

In one aspect, the disclosure provides a battery management system,comprising a first battery module, a second battery module, and a firstconverter. The first battery module has a first plurality of batterycells, including a first battery cell and a second battery cell. Thesecond battery module has a second plurality of battery cells, includinga third battery cell and a fourth battery cell. The first converter iselectrically connected to both the first battery cell and the thirdbattery cell. The first converter is configured to increase or decreasethe voltage between the first battery cell and a bus bar.

In another aspect, the disclosure provides a battery management system,comprising a first battery module, a second battery module, and a firstconverter. The first converter is electrically connected to at least onebattery cell of the first plurality of battery cells and a secondconvers is connected to at least one battery cell of the secondplurality of battery cells. The first converter and the second converterare both connected to a bus bar. The bus bar is configured to transfercharge between the at least one battery cell of the first plurality ofbattery cells and the at least one battery cell of the second pluralityof battery cells.

In another aspect, the disclosure provides a battery management system,comprising a first battery module, a second battery module, and abuck-boost converter. The buck-boost converter is electrically connectedto at least one battery cell of the first plurality of battery cells andat least one battery cell of the second plurality of battery cells. Thebuck-boost converted is configured to balance the level of chargeamongst both the first plurality of battery cells and the secondplurality of battery cells. Additionally a bus bar is connected to thebuck-boost converter and the bus bar is also connected to at least oneaccessory.

While various embodiments have been described, the description isintended to be exemplary, rather than limiting and it will be apparentto those of ordinary skill in the art that many more embodiments andimplementations are possible that are within the scope of theembodiments. Accordingly, the embodiments are not to be restrictedexcept in light of the attached claims and their equivalents. Also,various modifications and changes may be made within the scope of theattached claims.

We claim:
 1. A battery management system, comprising: a first batterymodule having a first plurality of battery cells, including a firstbattery cell and a second battery cell; a second battery module having asecond plurality of battery cells, including a third battery cell and afourth battery cell; and a bi-directional balancing circuit electricallyconnected to both the first battery cell and the third battery cell,wherein the bi-directional balancing circuit is an integrated circuitconfigured to transfer charge between at least the first battery celland the third battery cell.
 2. The battery management system accordingto claim 1, wherein the bi-directional balancing circuit is a buck-boostconverter.
 3. The battery management system according to claim 2,wherein the buck-boost converter is configured to increase or decreasethe voltage between the first battery cell and a bus bar.
 4. The batterymanagement system according to claim 1, wherein the bi-directionalbalancing circuit is configured to transfer charge from the firstbattery cell to the third battery cell and from the third battery cellto the to the first battery cell and, wherein the bi-directionalbalancing circuit is electrically connected to the fourth battery cell,and wherein the bi-directional balancing circuit is configured totransfer charge from the third battery cell to the fourth battery celland from the fourth battery cell to the third battery cell.
 5. Thebattery management system according to claim 1, wherein thebi-directional balancing circuit is electrically connected to the secondbattery cell, and wherein the bi-directional balancing circuit isconfigured to transfer charge from the second battery cell to the thirdbattery cell and from the third battery cell to the second battery cell.6. The battery management system according to claim 5, wherein thebi-directional balancing circuit is configured to transfer charge fromthe first battery cell to the second battery cell and from the secondbattery cell to the first battery cell.
 7. The battery management systemaccording to claim 1, wherein the bi-directional balancing circuit iselectrically connected to the first plurality of battery cells, andwherein the bi-directional balancing circuit is configured to transfercharge from the first plurality of battery cells to the third batterycell.
 8. The battery management system according to claim 7, wherein thebi-directional balancing circuit is configured to transfer charge fromthe third battery cell to the first plurality of battery cells.
 9. Thebattery management system according to claim 1, wherein the batterycells of the first plurality of battery cells are electrically connectedto each other in series and wherein the battery cells of the secondplurality of battery cells are electrically connected to each other inseries.
 10. The battery management system according to claim 1, furthercomprising: a third battery module having a third plurality of batterycells including a fifth battery cell and a sixth battery cell, whereinthe bi-directional balancing circuit is electrically connected to thefifth battery cell, and wherein the bi-directional balancing circuit isconfigured to transfer charge from the first battery cell to the fifthbattery cell and from the fifth battery cell to the first battery cell.11. A battery management system, comprising: a first battery modulehaving a first plurality of battery cells; a second battery modulehaving a second plurality of battery cells; and a bi-directionalbalancing circuit electrically connected to at least one battery cell ofthe first plurality of battery cells and at least one battery cell ofthe second plurality of battery cells, wherein the bi-directionalbalancing circuit is an integrated circuit configured to transfer chargebetween the at least one battery cell of the first plurality of batterycells and the at least one battery cell of the second plurality ofbattery cells.
 12. The battery management system according to claim 11,wherein the bi-directional balancing circuit is electrically connectedto each battery cell of the first plurality of battery cells and witheach battery cell of the second plurality of battery cells, and whereinthe bi-directional balancing circuit is configured to transfer chargefrom the first plurality of battery cells to the second plurality ofbattery cells.
 13. The battery management system according to claim 12,wherein the bi-directional balancing circuit is configured to transfercharge from the second plurality of battery cells to the first pluralityof battery cells.
 14. The battery management system according to claim11, wherein the battery cells of the first plurality of battery cellsand the battery cells of the second plurality of battery cells areLithium-ion battery cells.
 15. The battery management system accordingto claim 11, further comprising: a monitoring circuit electricallyconnected to least one battery cell of the first plurality of batterycells and electrically connected to at least one battery cell of thesecond plurality of battery cells, wherein the monitoring circuit isconfigured to monitor the status of charge of the at least one batterycell of the first plurality of battery cells and the at least onebattery cell of the second plurality of battery cells.
 16. The batterymanagement system according to claim 13, further comprising: amicroprocessor in serial communication with the monitoring circuit, suchthat the microprocessor receives at least one of voltage, current, andtemperature information about at least one cell of the first pluralityof battery cells and the second plurality of battery cells, and whereinthe microprocessor is in serial communication with the balancing circuitto balance the level of charge within the first plurality of batterycells and the second plurality of battery cells.
 17. A batterymanagement system, comprising: a first battery module having a firstplurality of battery cells; a second battery module having a secondplurality of battery cells; and a bi-directional balancing circuitelectrically connected to at least one battery cell of the firstplurality of battery cells and at least one battery cell of the secondplurality of battery cells, wherein the bi-directional balancing circuitis an integrated circuit configured to balance the level of chargeamongst both the first plurality of battery cells and the secondplurality of battery cells.
 18. The battery management system accordingto claim 17, further comprising: a monitoring circuit electricallyconnected to each battery cell of the first plurality of battery cellsand electrically connected to each battery cell of the second pluralityof battery cells, wherein the monitoring circuit is configured tomonitor the status of charge of the battery cells of the first pluralityof battery cells and the battery cells of the second plurality ofbattery cells.
 19. The battery management system according to claim 18,wherein the monitoring circuit is configured to detect which batterycells of both the first plurality of battery cells and the secondplurality of battery cells have excess charge, and wherein the balancingcircuit is configured to distribute the excess charge amongst thebattery cells of the battery cells of both the first plurality ofbattery cells and the second plurality of battery cells that do not haveexcess charge.
 20. The battery management system according to claim 17,further comprising: a microprocessor in serial communication with themonitoring circuit, such that the microprocessor receives at least oneof voltage, current, and temperature information about at least one cellof the first plurality of battery cells and the second plurality ofbattery cells, and wherein the microprocessor is in serial communicationwith the balancing circuit to implement a balancing algorithm thatbalances the level of charge within the first plurality of battery cellsand the second plurality of battery cells.